Peculiar light emission properties have been observed in cylindrical microcavity hosting dye-doped helixed liquid crystals, which behaves as a fiber-like multidirectional distributed feedback laser. Experimental studies performed for this level of confinement show that laser action is exhibited both axially and radially, indicating a self-organized three-dimensional blue phase-like configuration. Thermal wavelength tunability was observed for both orientations emphasizing two different linear behaviors. The distributed feedback mechanism and the factor of the mirrorless resonant cavity result enhanced for axial stimulated emission because of the significant increase in the number of helical periods. In addition, long-lived spectrally narrow defect modes appear within the photonic band gap owing to optical phase jumps which take place in local structuraldefects.

An efficient routing of surface plasmonpolaritons (SPP) is of fundamental importance in the development of SPP-based photonics. This paper reports that microgratings acting as Bragg mirrors can guide SPP along metal stripes waveguides featuring 90° bents. The measurement of the mirrors efficiency, performed by means of photon scanning tunneling microscopy, shows that bent losses as low as can be achieved. Finally, we demonstrate operating SPP beamsplitters obtained by an appropriate design of the Bragg mirrors constituting elements.

A large negative lateral shift of a light beam reflected from the so-called Kretschmann–Raether configuration containing left-handed material is predicted due to the formation of the unusual standing wave. An analytical resonant condition is given when there is a large negative lateral shift.

Single-layer high-efficiency green electrophosphorescent light-emitting diodes were fabricated by doping an iridium complex bearing pinene group—tris(5-phenyl-10,10-dimethyl-4-aza- tricycloundeca-2,4,6-triene)Iridium(III)—into a blended host of poly(vinylcarbazole) and 2-(4-biphenylyl)-5-(4-tert-butulphenyl)-1,3,4-oxadiazol. The optimized device shows a turn-on voltage below 4 V, and a very high peak luminescent efficiency of . Comparing with the state-of-the-art electrophosphorescent devices, the present device has a much slower decrease of efficiency with increase of current density; a high efficiency of can still be achieved at a high current density of .

An ultracompact siliconelectro-opticmodulator was experimentally demonstrated based on siliconphotonic crystal(PhC)waveguides for the first time to our knowledge. Modulation operation was demonstrated by carrier injection into an -long siliconPhCwaveguide of a Mach-Zehnder interferometer (MZI) structure. The phase shift driving current, , across the active region is as low as , which is equivalent to a of when a impedance-matched structure is applied. The modulation depth is 92% operating at .

Photosensitive sol-gel hybrid materials (hybrimers) exhibited a thick filmproperty, an efficient refractive index tunability through the control of their compositions, and a high photosensitivity upon UV exposure. The materials were used for the direct photofabrication of the multimode optical waveguide (MOW) with a large core structure. Due to the outstanding optical properties of these materials, problems and complexities associated with the fabrication of MOW could be overcome, and a MOW with good propagation performance could be easily fabricated. Importantly, a propagation loss of as low as at could be obtained.

We investigate an external cavity curved two-section mode-locked diode laser system based on quantum-dot (QD) gain media near . Pulses are generated from the external laser cavity at a repetition rate and amplified using a multilayer quantum-dot semiconductor optical amplifier. The pulses are compressed with a dual-grating dispersion compensator. The shortest, near transform-limited pulses are obtained when the mode-locked pulses are positive (up) chirped. The compressed pulses are in duration, with a pulse energy of , implying a peak power of .

Peculiar light emission properties have been observed in cylindrical microcavity hosting dye-doped helixed liquid crystals, which behaves as a fiber-like multidirectional distributed feedback laser. Experimental studies performed for this level of confinement show that laser action is exhibited both axially and radially, indicating a self-organized three-dimensional blue phase-like configuration. Thermal wavelength tunability was observed for both orientations emphasizing two different linear behaviors. The distributed feedback mechanism and the factor of the mirrorless resonant cavity result enhanced for axial stimulated emission because of the significant increase in the number of helical periods. In addition, long-lived spectrally narrow defect modes appear within the photonic band gap owing to optical phase jumps which take place in local structuraldefects.

We used a double tweezers setup to perform ultrasensitive force spectroscopy and observe the forces due to light scattering in a single isolated particle. We demonstrate how to selectively couple the light to the transverse electric (TE), transverse magnetic (TM), or both TE and TM microsphere modes by means of the beampolarization and positioning, and to observe correspondent morphology-dependent resonances (MDR). The results show how the usually assumed azimuthal symmetry in the horizontal plane no longer holds because of the symmetry break caused by the beampolarization. Also, the MDR resonances can change the force values by more than 30–50%.

The resonant modes of two-dimensional planar photonic crystalmicrocavities patterned in a free-standing InP slab are probed in a novel fashion using a long working distance microscope objective to obtain cross-polarized resonant scattering and second-harmonic spectra. We show that these techniques can be used to do rapid effective assays of large arrays of microcavities that do not necessarily contain resonant light-emitting layers. The techniques are demonstrated using microcavities comprised of single missing-hole defects in hexagonal photonic crystal hosts formed with elliptically shaped holes. These cavities typically support two orthogonally polarized resonant modes, and the resonant scattering and harmonic spectra are well fitted using a coherent sum of Lorentzian functions. The well-defined coherence between the two resonant features is explained in terms of a microscopic harmonic oscillator model. The relative merits of these techniques are quantitatively compared with the more commonly used cavity-enhanced photoluminescence technique.

We employ two different methods to generate controllable elliptical polarization of teraherz (THz) pulses. First, THz pulses are generated via optical rectification in nonlinear crystals using a pair of temporally separated and perpendicularly polarized optical pulses. The THz ellipticity is controlled by adjusting the relative time delay and polarization of the two optical pulses. We generate mixed polarization states of single-cycle THz pulses using ZnTe, and elliptically polarized multicycle THz pulses in periodically poled lithium niobate crystals. Second, we generate elliptically polarized THz pulses by making a THz “wave plate” using a combination of a wire-grid THz polarizer and a mirror to transform linearly polarized multicycle THz pulses into elliptical polarization.

A lensless tunable external-cavity laser diode monolithically integrated with InP-based planar waveguide parabolic-shaped collimating lens, optical deflector, and echelle grating is proposed and demonstrated in this work. The tunable laser exhibits a total wavelength tuning range of 9.3 nm with a side mode suppression ratio of about 35 dB by adjusting the applied current of optical deflectors and phase control section.

We have demonstrated that single crystals of a thiophene/phenylene co-oligomer [-bis-biphenyl-4-yl-terthiophene (BP3T)] show interesting photonic aspects: (1) the self-waveguided amplified spontaneous light emissions with a comparable low threshold of to other optimized organic solid-state laser systems, and (2) the laser oscillation based on the optical self-confinement effect in the crystals. We have also presented electroluminescence from the crystals based on bipolar injection and the crystals’ tolerance for intense current driving. These achievements strongly imply that BP3T crystals are a promising candidate for organic laser diodes.

The luminescent properties of conjugated polymers are seriously affected by concentration of the conjugated chains and the degree of polymer chain packing. We examined the effect of nanoporous morphology in the emitting layer of poly[2-methoxy-5-(-ethylhexyloxy)-1,4-phenylene vinylene] to hope that it would prevent polymer chain packing so that effectively decrease interchain interaction caused by interchain species and aggregates. High luminance is obtained at relatively low current density since the annihilation of singlet excitons is decreased. Redshifted emission due to the interchain aggregates and excimers are also suppressed, so that the color purity of the devices is greatly improved.

The effect of combining plasma and photocatalyst for Volatile Organic Compounds (VOC) removal was investigated in a pulsed low-pressure dc discharge. The photocatalyst was while the VOC was acetylene (1000 ppm) diluted in dry air. The temporal evolution of concentration was measured by Tunable Diode Laser Absorption Spectroscopy (TDLAS) in the mid-infrared region during the plasma pulse (one second). The contribution of external ultraviolet radiation and plasma exposure were quantified, both with and without a photocatalyst. The synergetic effect was clearly demonstrated.

Amorphous Nb–Si alloys have a temperature-dependent resistivity which can be tuned over many decades by controlling composition and are used for thin-filmthermometers.Annealing at temperatures from 100 to 500 °C produces dramatic but easily controlled increases in resistivity, both magnitude and temperature dependence, for insulating and metallic samples with compositions ranging from 8–15 at. %Nb. A transition from metal to insulator is induced by annealing an initially metallic sample. Annealing produces thermal stability against subsequent heat treatment, allowing annealed films to be used as low-temperature thermometers even when they are cycled to temperatures as high as 500 °C. Cross-section transmission electron microscopy and energy-dispersive x-ray analysis show that the initially amorphous films develop Nb-rich clusters within an amorphous Nb-depleted matrix, explaining the observed resistivity increase.

We show that B clusters, produced by self-interstitial interaction with substitutional B in crystalline Si, dissolve under annealing according to two distinct paths with very different characteristic times. The two regimes generally coexist, but while the faster dissolution path is predominant for clusters formed at low B concentration , the slower one is characteristic of clusters formed above the solubility limit and dominates the dissolution process at high B concentration . The activation energies of both processes are characterized and discussed. It is showed that the faster path can be connected to mobile B direct emission from small clusters, while the slower path is demonstrated not to be self-interstitial limited and it is probably related to a more complex cluster dissolution process.

The structure and composition of threading dislocations in GaN grown by hydride vapor phase epitaxy have been examined by electron microscopy. Transmission electron microscopy showed that the core structure of screw dislocations varied widely, alternating irregularly between open core (“nanopipe”) and closed core structures, with evidence that the equilibrium structure was a closed core configuration. A combination of electron energy loss spectroscopy and atomic resolution imaging in the scanning transmission electron microscope showed that the surfaces of nanopipes had monolayers of nitrogen substituted by oxygen, and that closed core dislocations showed little evidence of oxygen segregation. It is argued that these results support a model where nanopipe formation is controlled by the segregation of oxygen by surface diffusion to surface pits, rather than dislocationsper se. The implications for understanding the electronic properties of dislocations in GaN are discussed.

Heavy metal-oxide glasses containing lead and bismuth were prepared, and their picosecond third-order nonlinear (NL) optical characteristics were investigated. NL refractive indices of at were measured. Negligible NL absorption was verified and, as a consequence, the samples present a good factor-of-merit for photonic applications.

Based on the model that the high-pressuremeltingtemperatures of metals approximately equal the experimentally measuredinterfacetemperatures between the metallic plate sample and the transparent window when shock- and/or release-induced melting falls into the mixed phase region, we proposed a method to determine the meltingtemperatures of metals under megabars of shock compression. Experiments were conducted by using the oxygen-free high-conductivity copper, and pure iron plate sample with single-crystal lithium fluoride windows. Results showed that the measuredmeltingtemperatures are in good agreement with reported theoretical calculations.